Benson, Simon. W. L. Thompson, R. A. Booth, and Herbert Nunn. Third Biennial Report of the Oregon State Highway Commission Covering the Period December 1st, 1916 to November 30th, 1918. Salem: State Printing Department. 1919 (Reprinted by Project Gutenberg: http://www.gutenberg.org/files/35344/35344-h/35344-h.htm)
Past and Present Views Along the Columbia River Highway
Brian Colburn, March 21, 2021:
1895 map of Clatsop County. It shows several roads that appear to have been incorporated into the Lower Columbia River Highway. This map can be downloaded as a small map or a very large, highly detailed tiff file.